Method of drawing and heat treating synthetic filaments

ABSTRACT

A method of drawing and heat treating undrawn filaments of condensation polymer between a heated feed roller rotating at a constant peripheral speed and a draw roller rotating a constant peripheral speed greater than that of the former, the surface of said feed roller being heated at a temperature within the range of from the second order transition point of said filaments to a temperature 55* C. higher than the second order transition point, characterized in that, A. A PRESSURE ROLLER IS PROVIDED WHICH ROTATES BY CONTACTING WITH THE AFORESAID HEATED FEED ROLLER AND PRESSES AGAINST AT LEAST THE FINAL TURN OF THE FILAMENT WOUND AROUND THE HEATED FEED ROLLER TO THEREBY FIX THE NECKING POINT AT THE POINT OF CONTACT OF THE TWO ROLLERS; AND B. A SLIT HEATER HAVING A GROOVE WIDTH OF 0.5-3.0 MM IS DISPOSED BETWEEN THE HEATED FEED ROLLER AND THE DRAWING ROLLER, THE TEMPERATURE (Y* C.) of the slit heater and treating time (x sec.) being so chosen as to satisfy the following conditions: y &gt; OR = -1770.8 x + 255, 100 &lt; OR = y &lt; OR = 400, and 0.01 &lt; OR = x &lt; OR = 0.12.

United States Patent Fukushima et a1.

[ June 20, 1972 [54] METHOD OF DRAWING AND HEAT TREATING SYNTHETIC FILAMENTS [73] Assignee: Teijin Limited, Osaka, Japan [22] Filed: June 29, 1970 [21] Appl. No.: 50,809

Related US. Application Data [63] Continuation-impart of Ser. No. 658,799, Aug. 7,

1967, Pat. No. 3,539,680.

FOREIGN PATENTS OR APPLICATIONS 1,491,957 8/1967 France.. ..264/29O 38/2022 3/1963 Japan ..264/210 Primary Examiner-Jay H. Woo Attorney-Shermand and Shalloway 57 ABSTRACT A method of drawing and heat treating undrawn filaments of condensation polymer between a heated feed roller rotating at a constant peripheral speed and a draw roller rotating a constant peripheral speed greater than that of the former, the surface of said feed roller being heated at a temperature within the range of from the second order transition point of said filaments to a temperature 55 C. higher than the second order transition point, characterized in that,

a. a pressure roller is provided which rotates by contacting with the aforesaid heated feed roller and presses against at least the final turn of the filament wound around the heated feed roller to thereby fix the necking point at the point of contact of the two rollers; and

b. a slit heater having a groove width of 0.5-3.0 mm is disposed between the heated feed roller and the drawing roller, the temperature (y C.) of the slit heater and treating time (x sec.) being so chosen as to satisfy the following conditions: y 1770.8 255, 100 s y s 400, and 0.01 E x e 0.12.

5 Claims, 6 Drawing Figures PATENTEnJum I972 3,671,623

SHEET 30F 3 IOO 06s I I (sec).

METHOD OF DRAWING AND HEAT TREATING SYNTHETIC FILAMENTS This application is a continuation-in-part of our copending application, Ser. No. 658,799, filed Aug. 7, 1967 and now US. Pat. No. 3,539,680, issued Nov. 10, 1970.

This invention relates to a method of drawing and heat treating synthetic filaments of condensation polymers; especially polyester or polyamide filaments.

In a prior continuous drawing and heat treating process, undrawn filaments are fed from a feed roller around a snubbing pin, and then they are contacted with a heated plate, followed by drawing with a draw roller which is rotating at a peripheral speed different from the peripheral speed of the feed roller.

However, such a drawing and heat treating process sufiers certain disadvantages. In particular when high drawing speeds are used and when the total denier of the undrawn filaments is large, a large number of wraps around the hot pin is required in order to impart sufficient heat to the filaments necessary for drawing. However, due to frictional resistance of the pin, there is a limit to the number of wraps that can be provided around the pin. Thus, the heating becomes insufficient or ununiforrn. Further, there has been the disadvantage that friction can cause undesirable properties in the filaments. In particular the necking point tends not to be fixed, but fluctuates thus causing fluffs(fuzzes) and unevenness in dyeing. Further, abrasion of the hot pin per se readily takes place with the result that the pin has to be renewed at intervals.

Moreover, the fluctuation in tension during heat treatment become great depending upon various variations such as those of the wear the tear of the heated plate surface, the degree of pressing contact of the traveling filaments with the heated plate, the superficial condition of the filament itself, and the amount of lubricant on the filaments. As a result, the quality of the resulting heat treated filaments becomes nonuniform.

In order to eliminate said disadvantages which attend the heat treatment carried out by means of contact with the heated plate, much effort is required such as exchanging the heated plate before its superficial wear and tear becomes excessive or exercising strict control over the surface temperature of the heated plate. In consequence, much labor and expenses are required for eliminating the aforesaid disadvantages during the actual manufacturing process.

In addition, as methods for minimizing the fluctuations in the tension during heat treatment, also conceivable are such methods as providing a bath of heated gas or liquid and passing the filaments through such a bath, or directly heating the traveling filaments by means of infrared rays. However, in either case it is extremely uneconomical, since the equipment and expenses required for carrying out the uniform heat treatment at high speeds with the numerous spindles involved are enormous.

A primary object of the present invention is to provide a method of drawing and heat treating whereby synthetic filaments of polycondensed polymers can be uniformly drawn and heat treated to obtain good quality yarn which is without fluffs and can be evenly dyed. Another object is to provide a drawing and heat treating method which can carry out the drawing and heat treating the filaments at a higher speed than that of the conventional methods. A further object is to provide a method of drawing and heat treating which has advantages from the standpoint of equipment requirements.

The foregoing objects of the present invention are achieved by a method of drawing and heat treating undrawn filaments of condensation polymer between a heated feed roller rotating at a constant peripheral speed and a draw roller rotating a constant peripheral speed greater than that of the former, the surface of said feed roller being heated at a temperature within the range of from the second order transition point of said filaments to a temperature 55 C. higher than the second order transition point, characterized in that,

a. a pressure roller is provided which rotates by contacting with the aforesaid heated feed roller and presses against at least the final turn of the filament wound around the heated feed roller to thereby fix the necking point at the point of con tact of the two rollers; and

b. a slit heater having a groove width of 0.5 3.0 mm is disposed between the heated feed roller and the drawing roller, the temperature (y C.) of the slit heater and treating time (x second) being so chosen as to satisfy the following conditions;

y *l770.8 x+ 255 100 e y s 400 0.01 5 x 0.12

(wherein y is the temperature C.) of the slit heater, x is the treating time (second) obtained by dividing the effective heating groove length of the slit heater by thetraveling speed of the filaments.)

The polycondensed polymers of which the undrawn filaments to be drawn and heat treated by the method of this invention are composed may be such, for example, as polyesters, polyamides and polycarbonates, or copolymers in which these predominate. These undrawn filaments can be obtained by melt-spinning these polymers in customary manner. The preferable filaments used in the present invention are filaments whose denier per monofilament is below 150. Among those undrawn filaments, filaments composed of polyesters are most preferable.

Polyester filaments used in the present invention contain not less than mol percent of ethylene terephthalate units, and as the other acid component, a dibasic acid such as phthalic acid, isophthalic acid, adipic acid, oxalic acid, sebacic acid, suberic acid, glutaric acid, pimelic acid, fumaric acid and succinic acid is used. A polymerization degree modifier like propionic acid may be included. As alcohol component, a divalent alcohol such as polymethylene glycol having two-l0 carbon atoms (trimethylene glycol and butylene glycol) and cyclohexane dimethanol may be cited, and they may contain a small amount of any of the following compounds as a modifier, 5-oxydimethyl isophthalate, 5-oxydimethyl hexahydroisophthalate, benzenel ,3 ,S-tricarboxylic acid, paracarbomethoxy phenyl diethyl phosphonate, 3,5- dicarboxy phenyl diethyl phosphonate, pentaerythritol, glycerol, glucose, phosphoric acid, triphenyl phosphate, tri-pcarbomethoxy phenyl phosphate, triphenyl phosphinat'e, triphenyl arsenite, tricapryl borate, sorbitan, trimesic acid and diethylene glycol.

Although this invention may be applied to various polyesters described above, it is especially suitable for the drawing of filaments composed of polyethylene terephthalate alone.

The cross sectional configuration of polyester filaments usable in the present invention may be normal circular, non-circular (triangular, pentagonal, flat, cross, etc.), hollow (doughnut, non-circular hollow). Especially when filaments having non-circular or non-circular hollow cross sectional configuration are drawn by the conventional drawing and heat treating process, fluffs and dyeing unevenness increase, however, according to the process of the present invention, it is possible to carry out drawing and heat treating of such filaments without being said disadvantage.

A preferred embodiment of the invention will be fully described with reference to the accompanying drawings, in which:

FIGS. 1 and 2 are schematic front and side views, respectively, of an embodiment of the present invention;

FIGS. 3 and 4 are views illustrating one example of a slit heater, FIG. 3 being a cross-sectional view at right angles to the direction of travel of the filaments and FIG. 4 being a view in vertical section as seen from the front in parallel to the direction of the travel of the filaments;

FIG. 5 is a graph showing the scope of the heat-treating temperature and treating time in this invention; and FIG. 6 is a view illustrating the relative positions of the heated feed roller and the pressure roller.

Referring to FIGS. 1 and 2, undrawn filaments 2 are wound about a bobbin 1. The undrawn filaments 2 are fed from the bobbin 1 with a guide to a delivery roller 3 rotating at a predetermined speed and co-operating with a nip roller 4 arranged thereabove. The filaments 2 are fed from the roller 3 to a cylindrical heated feed roller 6 which is fixedly mounted on a positively driven rotary shaft (not shown). The feed roller 6 has arranged therein a heating member (not shown) which maintains the peripheral surface of the roller at a predetermined temperature. The heated feed roller 6 rotates at a peripheral speed slightly higher than that of the delivery roller 3, thereby imparting necessary pre-tension to the filaments. In the vicinity of the heated feed roller 6, a separator roller 8 is mounted and the filaments are wrapped around the heated feed roller 6 and separator roller 8 the required number of times to heat the filaments and prevent them from slipping. The numeral 7 represents a freely rotatable pressure roller having an elastic outer surface which is in contact with the outer surface of the heated feed roller 6 and rotated, thereby pressing upon either several wraps of filaments containing at least the last wrap of filaments about to depart from the heated feed roller or only the last wrap on to the heated feed roller, whereby the necking point is definitely fixed at the contact point of the two rollers without fluctuation. Below the heated feed roller 6, a slit heater 9 is provided, and further thereunder a draw roller 10 and a separator roller 11 for the draw roller are provided. The filaments are pulled from the feed roller by the drawing roller 10 and drawn. The filaments are heat-treated by the slit heater 9.

As shown in FIGS. 1 and 2 the slit heater 9 comprises a longitudinal body having a lagged metal portion heated for instance, electrically and provided with a longitudinal duct or channel open at both ends through which the filaments pass, the channel having a slit extending along its length for facilitating stringing up the filaments prior to stretching.

In practising the process, it is necessary that the surface temperature (1 C.) of the heated feed roller should be within the range of Tg C. to (Tg 55 C. where Tg C. is the second order transition point of the undrawn filaments. When T C. becomes lower than Tg C., heat necessary for drawing is not imparted to the undrawn filaments, and as a result, dyeing unevenness is brought about in the drawn filaments. When T becomes higher than (Tg 55) C., the undrawn filaments stick to one another by fusing and crystallize partially; then drawing all the filaments without any breaking becomes difficult. A preferable range of T is from (Tg 5) C. to (Tg According to the present invention, the filaments which have been drawn are heat treated by means of a slit heater under the following conditions.

FIGS. 3 and 4 illustrate one embodiment of construction of the slit heater, the figures being respectively a cross-sectional view at right angles to the direction of travel of the filaments and a vertical sectional view as seen from the front in parallel to the direction of travel of the filaments. The slit heater is made up of a grooved block 16 having an internally disposed heating source 17, heat insulating material 12 and grooved block case 13 provided with slopes 14 to facilitate the introduction of the filaments into the groove. As shown in FIGS. 3 and 4, the groove is either U-shaped or U-shaped and has a groove width a, groove depth b and an effective heating groove length 0 in the direction of travel of the filaments. The filaments to be treated run through the central part of the groove without touching the wall of the groove.

The reason why a slit heateris used in the drawing and heat treating method of the present invention is for ensuring that the filaments which have been uniformly drawn are caused to travel through the slit heater in a state of non-contact with the walls of the groove to thus prevent the fluctuation in tension during the heat treatment operation. Further, the heat treatment of the filaments can be carried out by using the slit heater which has a groove width of 0.5 3.0 mm uniformly and most efficiently without the filaments touching the inner walls of the groove.

TABLET Groove length (0) mm.

Groove Groove depth (b) mm.

width,

Filament tension, gJDe. (8) mm. 5 10 20 30 5 10 20 30 7.0 6.8 6.8 6.0 6.3 6.1 6.2 6.1 V 0.30 0.24 0. 23 0. 21 0. 27 0. 27 0.25 0. 23 {X 7.1 7.0 7.1 7.1 6.4 6.4 6.3 6.3 V 0.28 0.24 0.22 0.20 0.20 0.23 0.20 0.20 {R 7.2 7.0 7.0 7.1 6.4 6.3 6.4 6. V 0.27 0.22 0. 20 0.21 0. 28 0. 24 0. 20 0.20 M l g g l H 7.2 7.1 7.1 7.0 6.5 6.4 6.4 6.4 Vv 0.28 0.21 0.21 0.18 0.23 0.23 0.20 0.1 {X 7.3 7.2 7.0 7.1 6.5 6.4 6.3 6.4 V 0.27 0.20 0.18 0.20 0.26 0.22 0.21 0.18 {Y 7.2 7.1 7.1 7.0 6.6 6.4 6.5 6. V 0.20 0.24 0.23 0.23 0.20 0.26 0.24 023 {Y 7.4 7.2 7.3 7.1 6.6 6.5 6.6 6.4 V 0.34 0. 20 0.28 0.28 0.33 0.26 0. 26 0.28 {X' 8.0 7.0 7.0 7.8 6.8 6.6 6.7 6.6 V 0.28 0.25 0.23 0.21 0.25 0.25 0. 24 0.2 {Y 8.2 8.1 8.0 8.0 6.9 6.8 6.7 6.8 Vv 0.26 0.24 0.10 0.20 0.23 0.21 0.21 0.20 F 82 8.1 8.0 8.1 6.0 6.8 6.8 6.7 Vv 0.26 0.22 0.20 0.10 0.27 0.20 0. 20 0.18 L5 7 L0 it 8.3 8.1 8.0 8.1 7.0 6.0 6.0 6.8

time satijylhe following conditions:

groove depth b and its efl'ective heating groove length in the direction of travel of the filaments, with the results shown in Table l.

The values in Table l are shrinkage in boiling water of the filaments which, after having been drawn under identical conditions, were heat treated by a slit heater having varying groove widths and depths (the heating temperature used being 200 C. and efiectivc heating groove length being 200 mm and 360 mm), these values being given to illustrate the effects of the heat treatment. '52 in the table is the arithmetic mean of the values of shrinkage in boiling water with respect to the measurements using six pirns, and W is the square root of mean square of the six measured values. Generally, the smaller the shrinkage in boiling water, the greater the heat treating effect. Further, a smaller value of {V means that a more uniform heat treatment is conducted. 7 7

As shown in Table I, when the depth and length of the groove are constant, the heat setting effect becomes smaller as the groove width a increases. However, a worthy fact is that when the groove width 0 exceeds i0 mm the degree of variation of heat treatment effect (V V) becomes greater without being bytlir depth or length om; groove. 0n the other hand, when the groove width is less than 0.5 mm, the degree of variation in the heat setting efiect among the pirns also becomes great, since the adjustment of the running position of the filaments in the groove so as not to contact with the inn er walls ofjhe groove becomes very diflicult. While the desirable groove depth b will vary depending upon the groove width 0, because it is liable to be aflected by the outside atmosphere when depth b is less than mm, the heat setting effect is somewhat less than in the casewhere the depth b is greater than 5 mm and moreover the variation in the heat setting effect is also great. However, when that part of the slit heater which opens outwardly is sealed off by means of insulating material so as to leave only the slitted portion necessary for the travel of the filaments, the sufficient effect can be obtained even if the groove depth is less than 5 mm. On the other hand, it is seen that the heating groove length c in the direction of the travel of the filaments, in the case where the groove width and groove depth are constant, does not have much effeet on the degee of variation of the heat treating effect.

According to the invention, a slit heater having a groove width of 0.5 mm 3.0 mm, as hereinbefore indicated, is employed, and the heat treatment is carried out in such a manner that the heating temperature of this slit heater and the treating 100 S y 400 0.01 5. x 0.12 wherein y is the temperature C.) of the slit heater, and x is treating time (second) obtained by dividing the effective heating groove length of the slit heater by the traveling speed of the filament.

FIG. 5 is a graphic representation of the scope of the forgoing treating condition. The shaded portion of the graph encompasses the heating temperatures and treating times that are to be used in this invention.

Even when a slit heater of a slit width of 0.5 3.0 mm is used, if the above conditions are not satisfied, a good heattreating effect intended in this invention cannot be achieved.

When the heat treating time is less than 0.01 second, the

' heat treating efiect becomes inadequate, and the shrinkage in boiling water of the treated filaments becomes high. 0n the other hand, when the heat treatment time exceeds 0.12 second, fusing together of the individual filaments take place during the treatment Again, if the temperature of the slit heater exceeds 400 C., the degradation of filaments occurs. When the temperature of theslit heater falls to below 100 C., practically no heat treating effect is demonstrated.

Further, the heat treatment efiect is also unsatisfactory when the condition y a --l770.-8 .r 255 is not satisfied, the resulting treated filaments being undes'rable since their shrinkage in boiling water exceeds l0 percent. The heating temperature which is desirably used depends upon the class of the filaments to be treated. in the case of polyethylene terephthalate, it is 200 280 C., and in the case of nylon-6, it is 180 260 C. When the slit heater is set at these temperatures, the temperature of the filaments undergoing treatment becomes about C. lower than this, and a desirable heat treatment effect is obtained.

In a most preferable embodiment of the process of this invention, the drawing is carried out so as to meet the following requirements.

The first requirement is that the time (1 seconds) of the contact between the filament and the heated feed roller satisfies the condition expressed by the following formula depending n the surface temperature (1" C.) of the heated feed roller -O.l20)T- Tg) 28.420 B t z 0.003(T Tg) 0.189 preferably 0.l20(T- Tg) 7.72 e r z -0.003(T Tg) +0.189.

The second requirement is that the position of the contact point where the pressure roller contacts the surface of the heated feed roller shown in FIGS. 1 and 2 is set up within a specific range. Referring now to FIG. 6 which is an enlarged view of this portion, the position of the contact point is such that an angle a formed by a radius connecting a point B where the filaments would depart from the heated feed roller if the pressure roller were absent or in an inoperative position, with the center A of the heated feed roller and a radius connecting the contact point D with center A does not exceed 20.

When said angle a measured in the opposite direction of proceeding of the filaments exceeds 20 C, the necking point tends to fluctuate along the arc BD of the heated feed roller which causes non-uniform drawing.

As the angle 1: becomes greater, the distance along which the drawn portion of the filaments contacts the heated feed roller increases. Thus the appearance of flufis in the drawn filaments is invited by an action of rubbing filaments which is due to the difference between the peripheral speed of the roller and the linear travelling speed of the drawn portion of the filaments. 0n the other hand, when the angle a measured in the direction of proceeding of the filaments exceeds 20' C, the drawn filaments get in contact with the pressure roller, not with the feed roller. Since the elastic material covering the surface of the pressure roller has a relatively low hardness, the contact results in damage to the surface of the pressure roller which in turn causes flufi's to occur and further increases the chances of filament breakage. At the same time, it becomes necessary to frequently replace the pressure roller. Further, the necking point will again fluctuate with the result that drawing becomes non uniform, causing dyeing unevenness and the formation of flufis.

A preferable range of angle a is 0 to 3. By so doing, friction harmful to the filaments is minimized while maintaining sutficient heating and certain fixation of the necking point; as a result an excellent functional effect that makes it possible to carry out drawing at a high speed can be obtained.

A draw ratio which can be adopted in the process of the present invention is 2.0 6.0 and a drawing speed adoptable in the present invention is 50 m/min 4,500 m/min, namely, an operation at a draw ratio and a drawing speed higher than those normally adopted is possible in the present invention.

The third requirement is that before undrawn filaments pass round the heated feed roller, a predetermined pre-tension within the range of 10 percent of the tension at which the necking occurs in the drawing is imparted to said undrawn filaments. This tension at which the necking occurs in the drawing can be easily determined from the stress-strain curve of the undrawn filament obtained by conducting the tensile test of the said undrawn filament at a temperature of 20 C. and a relative humidity of 65 percent with the use of an Instron tester.

According to experimental results, when this pretension is less than 10 percent of the tension at which the neck occurs it becomes difficult to maintain the tension in the undrawn filaments at a predetermined value. On the other hand, when it is more than 90 percent of said tension, local drawing is carried out to bring about dyeing unevenness and occurrence of fluffs. Therefore, it is preferable that this pre-tension is within the range of 10 90 percent of the tension at which the neck occurs.

Heretofore as an apparatus to impart these pre-tensions, a thread brake and a guide have been used. However, it is difficult for them to impart uniform and predetermined tension to filaments. ln the present invention, in which the undrawn filaments are wrapped around the heated feed roller, in order to minimize the occurrence of fluffs and dyeing unevenness, it is especially required to feed said filaments under a predetermined tension. Therefore, it is preferable to securely hold and withdraw the filaments by using a combination of a roller and a delivery roller as shown in FIGS. 1 and 2. In order to impart a preferable pre-tension as mentioned above, the ratio of peripheral speeds of the delivery roller to the heated feed roller is generally within the range of l:l.00l 121.030. However, a thread brake or a guide may be used, if it can impart uniform and predeterminated tension.

In the apparatus used in the present invention, the urging of the pressure roller into contact with the heatedfeed roller, may-beeffected by known devices such as a spring, compressed air or oil pressure.

The peripheral surface of the pressure roller is made of a resilient material such as rubber, and the surface hardness of said elastic material, as measured by 118 (Japanese Industrial Standard) K-630l, is preferably 30 95. The surface of the heated feed roller may be smooth, or it may be matte.

Any suitable heating arrangement may be provided for heating the feed roller, for instance, an electrical heating means, a steam, a hot air, a heated medium or an infra-red radiation system may be used. Further, the heating may be effected from inside the roller, and the sealed surrounding space of the roller may be heated.

The following illustrative examples of the present inventions are given. In the several examples, the several measurement values were obtained in the following manner.

a. Method of measuring the second order transition point (Tg) Tg is as defined by A. Pace in U. S. Pat. No. 2,556,295. The measurement was carried out by the volume dilatometry method reported by Bekkedahl (J. Research N.B.S., 42 145 (1949). In the case of non-crystalline undrawn polyethylene terephthalate filaments, Tg is 69 C.

b. Method of measuring the intrinsic viscosity (1 of polyesters 1.25 percent of a sample was dissolved in O-chlorophenol at 100 C. The specific viscosity (f ap) of the so obtained solution was then measured at 35 C. and (1 was obtained as follows lim 1.

c. Method of measuring the birefringence (A n) The birefringence (A n) was measured with a polarization microscope having a crossed Nicol prism, as disclosed by A.N.J. Heyn (Textile Research Journal 22 5 l 3 (1952)). d. Method of measuring dyeing unevenness After knitting a sample, the knit test piece was dyed for 90 minutes at 100 C. in a dye solution (both ratio [:100) containing 3 percent of the dyestuff Dispersol Scarlet 8, based on the test piece. The dyeing unevenness of the dyed knit test piece was judged by the naked eye and the results were converted into N.B.S. units. The findings of the visual (necked eye) inspection were correlated to the N.B.S. ratings in the following manner e. Method of measuring the stress unevenness of the drawn filaments The stress unevenness was measured with the Elasticity Meter Dynagraph ll (manufactured by Herbert Stein Company). A sample filament was caused to travel at a measured speed of 24 meters per minute and a draw ratio of 10 percent, and the variation of the stress was continuously measured at this time. The difference between the maximum and minimum stresses of an 8-meter length of the sample filament was designated as R, which was continuously measured for 10 times (i.e. measuring 8 m X 10 m continuously). The average of several Rs thus obtained,

ii (E ght 1o =1 was designated the stress unevenness. I f. Method of measuring the fluffs of the drawn filaments The number of fiuffs per 1,000,000 meters of the drawn filaments was measured. g. Method of measuring the shrinkage in boiling water A sample filament was wound under an initial load expressed in terms of grams of 0.1 X (nominal denier of the filament) at a rate of 120 tums/min onto a sizing reel having a frame circuit of 1.125 m to form a small skein of 20 turns. A weight of a load 40 times as great as the initial load was imposed on the skein and the length of the skein was measured. Then, the load was released from the skein and it was lightly twisted, wrapped with a gauze cloth, and then dipped into boiling water for 30 minutes. Then, the sample was taken out from boiling water and air cooled. Then, the weight of a load 40 times as great as the initial load was imposed again on the sample and the skein length was measured. Then, the value of the shrinkage in boiling water was calculated by the following formula. The measuring was repeated 10 times and the mean value of the values obtained at each test was adopted.

Shrinkage in boiling water (percent) (I 11) ll X in which Idenotes the length (mm) of the skein before dipping in boiling water and I, denotes the length (mm) of the skein after shrinkage caused by dipping in boiling water.

EXAMPLES l 4 AND CONTROLS l 2 Polyethylene terephthalate chips having an intrinsic viscosity (1 of 0.65 were melted at 288 C., extruded through a spinneret having holes of 0.25 mm diameter, wound at a speed of 930 meters per minute to yield an undrawn yarn whose total denier was 261. The so obtained undrawn yarn had an intrinsic viscosity (1;) of 0.63, a second order transition point (Tg) of 69 C., a birefringence (An) of 549 X 10", and a tension at which the neck occurs of 0.36 g/d.

The so obtained undrawn yam was drawn using the drawing apparatus shown in FlGS. l and 2 while varying the surface temperature of the heated feed roll under the following conditions.

Pre-tension 0.10 g/d Draw ratio 3.67 X Drawing speed 500 m/min Diameter of the heated feed roll 100 mm Number of wraps of the yarn around the heated feed roll 7 Contact time of the yarn with the heated feed roll 0.775 see.

This was followed by heat treatment of the drawn yarn with a slit heater having an effective heating groove length of 300 mm groove depth of 20 mm and a groove width of 2.0 mm, which was heated to 260 C. The properties of the resulting drawn and heat treated yarn are shown in Table ll.

When the surface temperature of the heated feed roll was too low as in Control 1, the values of the dyeing unevenness and stress unevenness becomes very great. This indicates that the drawing was not carried out uniformly. It can be seen that TABLE II Surface temperature Elonge- Dyeing Stress Flufls per of heat roller Tenacity tion unevenuneven- 1,000,000 Experiment C.) (g./d.) (percent) ness ness (g.) In.

65 4. 78 26. 4 10. 36. 2 1. 2 70 4. 03 27. 3 1. 0. 0 0. 4 K0 5. ()3 27. 5 0. l 8. 3 0. 2 100 5. (ll 27. .l 1. (l 9. 2 0. 7 120 4. UK 27. J 2. 0 13. -l l. 0 (Tillltl'lll J. 125 -l.'.l.! 28.0 3.0 14.0 -l.'.!

there was an increase in the appearance of flufis when the temperature was too high as in Control ll.

EXAMPLES 5 6 AND CONTROLS 3 4 The drawing and heat treatment of filaments was carried out as in Example I. Sic pirns were obtained by an apparatus having a slit heater, as in Example l, and on the other hand, sic pirns are obtained by an apparatus having a 150 C. heated plate of steel with a sand-blasted surface of 300 mm effective contact length. The filaments obtained by drawing and heat treating the i'rlaments at a draw ratio of 3.60 X and drawing speeds of 300 and 600 meters per minute were measured for their drawing and fiber properties and the results shown in Table III were obtained.

treating apparatus having a slit heater as used in Example l. The temperature of the slit heater and the drawing speed (heat treatment time) were varied and the results shown in Table V, were obtained.

In the foregoing table, Examples 8 and 9 are experiments in accordance with the method of the present invention, whereas Controls 6 10 are without the scope of the invention. The former provides products having satisfactory quality. On the other hand, in any of Controls 6, 8 and 10, the value of the shrinkage in boiling water is high, and hence, it is apparent that in each of these controls the heat-setting effect is poor. Further, in Controls 7 and 9 filament breakages are caused to occur and formation of fluffs is extreme, resulting in decrease 2 5 in the amount produced of the product.

It is apparent from the results given in Table II! that the filaments obtained according to this invention are superior is drawability as well as uniformity of the product than the filaments obtained by the conventional method.

EXAMPLE 7 AND CONTROL 5 An undrawn yarn identical to that used in Example 1 was drawn and heat set under the following condition, employing the apparatus shown in FIGS. 1 and 2 except that the heatsetting device was changed.

Pre-tension 0.10 g/d Draw ratio 3.67 X

. Drawing speed v 800 m/min.

Diameter of heated feed roll 100 mm Surface temperature of heated feed roll 85 C.

When a comparison is made between instance where a slit heater having an effective length of 400 mm for heat setting was used with the instance where a heated plate was used, the results are as shown in Table IV. The temperature of the filament passing portion of the slit heater was 240 C., while the surface temperature of the heated plate was 160 C. V h H EXAMPLES 10- 1 1 AND CONTROLS l l 12 An undrawn 326 total denier 24 filaments poly e-capramide yarn having an intrinsic viscosity as measured in a m-cresol solution at 25 C. of 1.13, a second order transition point (Tg) of 37 C. and a birefringence of 15 X 10 was used as the sample. This yarn was drawn and heat treated at a draw ratio of 3.72 X'and drawing speeds of 300 and 600 metric per minute with a drawing and heat treating apparatus having a sandblasted cold drawing pin and a sand-blasted heated plate of carbon steel of efiective contact length of 500 mm, which was heated at 175 C. (controls).

On the other hand, a similar yarn was drawn and heat 'treated at a draw ratio of 3.27 X and drawing speeds of 300 and 600 meters per minute with a drawing and heat treating apparatus, such as shown in FIGS. 1 2, having a heated feed roll whose surface, was heated at C. and a slit heater hav' ing an effective heating groove length of 500 mm, groove depth of 20 mm and a groove width of 1.3 mm, which was heeL QaQQQiQ-Gra nie The so drawn and heat treated yarns were examined in each instance for their drawability and yarn properties and the results shown in Table VI were obtained.

Undrawn yarn of polyethylene terephthalate identical to that used in Example 1 was drawn with the drawing heat 1. In drawing and heat treating of undrawn synthetic filaments of condensation polymers between a heated feed roller rotating at a constant peripheral speed and a draw roller rotating at a constant peripheral speed greater than that of said ""041 nun-r TABLE V "ariatlon of I heater Heat Shrinkage shrinkage in Flufis tnmpar- Drawing setting in boiling boiling water per atu re speed time water among pirns 1,000,000 l'lxpm'lnmnt C.) (rm/min.) (seen) (percent) W (luntml (i 200 2, 300 0. C078 12. 3 0. 58 2. Example 8 260 000 0. 03 8. O 0. 34 0. 9 Control 7' 160 140 0. i3 6. 3 0.30 1.8 Control 8 210 010 0.02 11. 0 O. 49 l. 7 Example 1). A 210 600 0. 03 9. 1 0. 20 0. 7 Control J 210 140 0. 13 0. 27 1. 4 Control 10. 90 300 0. 06 13 2 0. 38 1.

Breakage oi filaments occurs.

TABLE VI Tension before en- Variation of trance to shrinkage in Drawing drawing boiling water Heat setting speed rollers among pirns Flufls per Experiment device (rn.min.) (g.) V 1,000,000m

Control 11. Heated plate 300 07 0. 22 0.8 Control 12. do 600 117 0. 30 1. 1 Example 10.. 800 89 0. 15 O. 4 Example 11 o, 600 102 0. 19 0. 4

heated feed roller, the surface of said feed roller being heated at a temperature (T C) within the range of the second order transitionpoint of said filament (Tg C) to a temperature 55 C. higher than the said second order transition point, the method which comprises a. providing a pressure roller which rotates by contacting said heated feed roller and presses at least the final turn of the filaments wound around said heated feed roller, thereby fixing the necking point at the point of contact of said pressure roller and heated feed roller; and

b. disposing between said heated feed roller and drawing roller a slit heater having a groove width of 0.5 3.0 millimeters, the temperature (y C) of the slit heater and treating time (x sec) being so chosen as to satisfy the following conditionsr y z l770.8 x 255 100 s y s 400 0.01 5 x S 0.12 2. The method of claim 1 wherein the time (t sec) of contact of said filaments with said heated feed roller is 0.120 (T-Tg) 28.420 2 r a -o.003 (T-Tg) 0.189

3. The met hod of claim iwherein said pressure roller a surface of elastic material andis so disposed in contact wigl 50 the periphery of said heated feed roller that its point of contact with said feed roller is positioned within a range of an angle a, said angle a being formed by a radius connecting said point of contact with the axial center of the heated feed roller and a radius connecting said axial center with the point at which the filaments depart from said heated feed roller when a pressure roller is not used, said angle a not exceeding 20, whereby said pressure roller presses the filaments in such a manner that at least the last wrap of said filaments wrapped around said heated feed roller is pressed against said heated sse5 1 1=L. .,W. t.

4. The method of claim 1 wherein said undrawn filaments are imparted a pretension prior to their entry to said heated feed roller, said pretension being within the range of 10 to percent of the tension at which the neck occurs as shown by a stress-strain curve of said undrawn filament measured at a temperature of 20 C. and a relative humidity of 65 percent.

5. The method of claim 1 wherein said undrawn filaments of condensation polymers are undrawn polyester filaments containing above 80 mol percent of ethylene terephthalate units, the monofilament denier of said filaments being below de mer.

i I i 

2. The method of claim 1 wherein the time (t sec) of contact of said filaments with said heated feed roller is 0.120 (T-Tg) + 28.420 > or = t > or = -0.003 (T-Tg) + 0.189
 3. The method of claim 1 wherein said pressure roller has a surface of elastic material and is so disposed in contact with the periphery of said heated feed roller that its point of contact with said feed roller is positioned within a range of an angle Alpha , said angle Alpha being formed by a radius connecting said point of contact with the axial center of the heated feed roller and a radius connecting said axial center with the point at which the filaments depart from said heated feed roller when a pressure roller is not used, said angle Alpha not exceeding 20*, whereby said pressure roller presses the filaments in such a manner that at least the last wrap of said filaments wrapped around said heated feed roller is pressed against said heated feed roller.
 4. The method of claim 1 wherein said undrawn filaments are imparted a pretension prior to their entry to said heated feed roller, said pretension being within the range of 10 to 90 percent of the tension at which the neck occurs as shown by a stress-strain curve of said undrawn filament measured at a temperature of 20* C. and a relative humidity of 65 percent.
 5. The method of claim 1 wherein said undrawn filaments of condensation polymers are undrawn polyester filaments containing above 80 mol percent of ethylene terephthalate units, the monofilament denier of said filaments being below 150 denier. 